hacking: update advice w.r.t. synced files

* HACKING: Update and improve advices and explanations about files
in the automake repository that are now owned by automake, but
mirrored from other upstreams.  Also, don't list these files
explicitly, rather point the reader to the $(FETCHFILES) variable
in Makefile.am.
* Makefile.am (FETCHFILES): Don't state that "there should be a
lot more here", as this is not true anymore today.  Only 'COPYING'
must be synced by hand.

1 files changed, 7 insertions, 7 deletions

diff --git a/HACKING b/HACKING
index ed78c9f7d..26f1d91e4 100644
--- a/HACKING
+++ b/HACKING
@@ -27,13 +27,13 @@
   sure to add a test case for it, and to reference such test case from
   a proper Texinfo comment.
 
-* Some files in the automake package are not owned by automake.  These
-  files should never be edited here.  These files are
-      COPYING (from FSF),
-      INSTALL (autoconf-patches@gnu.org),
-      config.guess, config.sub (config-patches@gnu.org),
-      texinfo.tex (bug-texinfo@gnu.org),
-  Most of them are updated before release with `make fetch'.
+* Some files in the automake package are not owned by automake; these
+  files are listed in the $(FETCHFILES) variable in Makefile.am.  They
+  should never be edited here.  Almost all of them can be updated from
+  respective upstreams with "make fetch" (this should be done especially
+  before releases).  The only exception is the 'lib/COPYING' (from FSF),
+  which should be updated by hand whenever the GPL gets updated (which
+  shouldn't happen that often anyway :-)
 
 * Changes other than bug fixes must be mentioned in NEWS.  Important
   bug fixes should be mentioned in NEWS, too.